Originally Posted by Raiyn
As with all things it depends where you buy themThey're pretty small so yes you could fit them in most under seat bagsDepends on the size and volume of the tire, also the pressure desiredNon-refillable. Generates a lot of waste (recyclable, but still)Modern hand pumps are simple to use. I prefer Crank Bros or Topeak
Actually they ARE refillable. You just need one badass compressor to do the job.
I have a friend who knows the people at the paintball shop. The compressors they use to refill the gun cartridges will also do bike CO2 cartridges.
For the original poster, the main point of the CO2 cartridges is a FAST refill. The target audience is racers (lazy people are the secondary audience).
If you are worried about refilling on trail after a flat, you may want to buy one of those "Seal n' flate" things with the latex. This will get you going again about as fast as anything.